everybody is twisting this discussion way beyond the scope of the opinions that have been shared. NO ONE in this thread has EVER stated that 80mph is not possible on a bicycle. obviously, it is. heck, google mile-a-minute murphy once. The ONLY point I ever tried to make was that an ht engine will probably never get you to 80mph under engine powwr alone, and that if it does, the engine may not survive it. Is it possible? maybe. but there is a difference between what an engine CAN do and what it is DESIGNED to do. ht engines were not DESIGNED to push a bicycle at 80mph by themselves, and therefore probably cannot handle the load that that kind of speed would put on the engine. There is a reason why mack truck engines are put in big rigs, and not hugo engines. this is almost the same concept. an ht is comparable to a hugo in the bicycle world. yes, you can draft a car or go down a steep hill. the point is, all those things have already been done WITHOUT engines. not to mention that a certain amount of torque is required for acceleration. at the gearing required to get an ht engine up to 80, the amount of torque required for the bike to accelerate would be extreme. so even while trying to get up to 80, you are already pushing the engine past its limits. now, if you had a car tow you to that speed and then let the engine take over, that is certainly possible. but thats the only way i see an ht engine getting to 80 UNDER ENGINE POWER. there are lots of other ways to get a bicycle to 80, but an ht engine will make no difference in those circumstances.